1. Field of the Invention
This invention relates to cathode ray picture tubes, and is addressed specifically to an improved device for centering picture tubes in the cabinets of television sets and other picture tube displays.
Cathode ray tubes (CRTs), especially those used in large-screen television sets, are bulky and awkward in shape, making them difficult to mount accurately in a cabinet. A CRT mounting and centering system preferably provides for easy, straight-forward installation of the tube. Most important, the system must be able to accommodate and compensate for the variances in the dimensions of rectangular face panels as measured along the diagonal. This dimension is termed the "diagonal fit dimension." By way of example, the variance in diagonal fit dimensions of the face panels of thirty-two inch tubes is in the range of .+-.0.118 inch. Face panels that measure at the low end of the range are designated as being of minimum diagonal measure, panels that measure at or near the center of the range are designated as being of nominal diagonal measure, and panels that measure at the high end of the range are designated as being of maximum diagonal measure. A face panel centering system must be able to accommodate the complete diagonal dimensional range from minimum to maximum.
The dimensions of cabinets in which CRTs are mounted may also vary, and a centering system that compensates for variances in the diagonal fit dimensions of the face panels preferably compensates for minor variances in the dimensions of the parts of the cabinet that mount the tube.
An additional requirement of a CRT mounting and centering system in strength. For example, the weight of a thirty-two inch tube is about 110 pounds, and the weight is concentrated largely in the face panel section of the tube. A tube centering system must be capable of supporting a face panel of this size and weight during installation of the tube.
2. Related Art
In commonly owned U.S. Pat. No. 4,360,838, there is disclosed an apparatus for mounting rectangular cathode ray picture tubes within the escutcheon of the picture tube cabinet. Cradles in each of the four corners of the escutcheon include guides which extend rearwardly from the opening in the escutcheon for guiding the corners of the face panel of the tube into the escutcheon. Tapered ribs which project from the cradling devices exert a progressively increasing force on the panel. As the corners of the panel are forced into the cradles by the pressure of the escutcheon, the tapered ribs are crushed to conform to the contour of the panel. By this means, slight but significant variances in the diagonal fit dimensions of face panels can be accommodated. A disadvantage inherent in this system lies in the fact that if it is necessary to replace a tube, the mounting system can accomodate tubes having panels of the same or larger diagonal measure, but not panels of smaller diagonal measure.
In U.S. Pat. No. 5,067,022 to Heurre et al, there is disclosed a fascia, or escutcheon, for a television set that includes a mechanism for centering at the four corners of the screen. The fascia has an inner rim which faces and contacts the screen. The centering mechanism comprises elastic tabs which are a part of the fascia and extend from the fascia at each corner, and are symmetrically arranged with respect to a bisector on each corner of the fascia. However, this fascia is operative only after insertion of the tube into the cabinet and is apparently directed toward centering the fascia about the viewing screen rather than centering the tube within the cabinet.
Other related art includes these U.S. Pat. Nos.--
3,142,203 to D'Angelo
3,643,020 to St. George et al
3,651,257 to Goetz
3,712,958 to Stute
4,247,871 to Hirsch